ahh yes your right kishi i forgot about that. but i think there wouldnt be enough of it to be used by many people, so that could be another excuse not to see materia in the movie. well, ff7 left a lot of open questions, so you could probably come up with many many many hypothesies (plural?) and find at least one piece of evidence for it
well in the latest trailer he showed up, jumping in front of a building, then that building comes crashing down and you get a good shot at him. but its still unclear whether that was a dream (definitely wasnt a flashback), and if it wasnt, i dont think it would be the old sephiroth we know, since vincent said "they could easily make another sephiroth if they wanted to" (refering to the 3 bad guys)